The invention relates to adaptive control of the operations of CNC operated machine tools wherein a feed rate of the CNC operated machine tool relative to a workpiece is continuously adjusted during a machining operation in response to inputs received from sensors regarding a load on a spindle drive.
In a CNC operated machine, a program for cutting the workpiece provides a feed rate to a feeding device instructing the feeding device to feed the machining tool used to cut into the workpiece at the specified feed rate. The feed rate and other parameters provided by the program are normally fixed based on expected pre-programmed cutting conditions, including the type of material to be machined, the type of tool used, and the cutting depth of the tool into the surface of the workpiece. However, conventional CNC operated machines do not take into consideration changes in these parameters either before or during the machining operation, and are thus unable to optimize the machining operation to increase efficiency of the machining operation as a whole.
State-of-the-art adaptive control methods for optimizing machining operations can adjust the feed rate of the machining operation based on various measurements and calculations performed during the machining operation. These optimizing methods noticeably improve the efficiency of the machining operation. Unfortunately, although the feed rate of the spindle drive can be continuously adjusted; such adjustments could become cyclical and induce a resonant vibration. If such vibration matches the resonance frequency or harmonics of the resonance frequency of the CNC operated machine or other components, the effect of the vibration can be amplified and could damage the machine, its components, and cause machining errors with the workpiece being machined at the time.
Similarly, when optimizing machining operations, it may seem counter-productive to permit an operator to over-ride the optimizing methods used by state-of-the-art adaptive control systems. As such, these systems typically operate with either the adaptive control methods enabled or disabled, but do not include the ability of the operator to adjust a target feed rate, target spindle load on the spindle drive, or other parameters which might adversely affect the CNC operated machines' ability to optimize the machining operations.
Lastly, some state-of-the-art optimizing systems have been implemented as external hardware or software add-ons retrofitted to existing CNC operated machines but not embedded into the device itself where it has access to all aspects of the system parameters.